/*
 *
 *  * Copyright (C) 2015 Square, Inc.
 *  *
 *  * Licensed under the Apache License, Version 2.0 (the "License");
 *  * you may not use this file except in compliance with the License.
 *  * You may obtain a copy of the License at
 *  *
 *  *      http://www.apache.org/licenses/LICENSE-2.0
 *  *
 *  * Unless required by applicable law or agreed to in writing, software
 *  * distributed under the License is distributed on an "AS IS" BASIS,
 *  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  * See the License for the specific language governing permissions and
 *  * limitations under the License.
 *
 */
package com.lark.oapi.okhttp.internal.io;

import com.lark.oapi.okio.Okio;
import com.lark.oapi.okio.Sink;
import com.lark.oapi.okio.Source;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;

/**
 * Access to read and write files on a hierarchical data store. Most callers should use the {@link
 * #SYSTEM} implementation, which uses the host machine's local file system. Alternate
 * implementations may be used to inject faults (for testing) or to transform stored data (to add
 * encryption, for example).
 *
 * <p>All operations on a file system are racy. For example, guarding a call to {@link #source}
 * with {@link #exists} does not guarantee that {@link FileNotFoundException} will not be thrown.
 * The file may be moved between the two calls!
 *
 * <p>This interface is less ambitious than {@link java.nio.file.FileSystem} introduced in Java 7.
 * It lacks important features like file watching, metadata, permissions, and disk space
 * information. In exchange for these limitations, this interface is easier to implement and works
 * on all versions of Java and Android.
 */
public interface FileSystem {

    /**
     * The host machine's local file system.
     */
    FileSystem SYSTEM = new FileSystem() {
        @Override
        public Source source(File file) throws FileNotFoundException {
            return Okio.source(file);
        }

        @Override
        public Sink sink(File file) throws FileNotFoundException {
            try {
                return Okio.sink(file);
            } catch (FileNotFoundException e) {
                // Maybe the parent directory doesn't exist? Try creating it first.
                file.getParentFile().mkdirs();
                return Okio.sink(file);
            }
        }

        @Override
        public Sink appendingSink(File file) throws FileNotFoundException {
            try {
                return Okio.appendingSink(file);
            } catch (FileNotFoundException e) {
                // Maybe the parent directory doesn't exist? Try creating it first.
                file.getParentFile().mkdirs();
                return Okio.appendingSink(file);
            }
        }

        @Override
        public void delete(File file) throws IOException {
            // If delete() fails, make sure it's because the file didn't exist!
            if (!file.delete() && file.exists()) {
                throw new IOException("failed to delete " + file);
            }
        }

        @Override
        public boolean exists(File file) {
            return file.exists();
        }

        @Override
        public long size(File file) {
            return file.length();
        }

        @Override
        public void rename(File from, File to) throws IOException {
            delete(to);
            if (!from.renameTo(to)) {
                throw new IOException("failed to rename " + from + " to " + to);
            }
        }

        @Override
        public void deleteContents(File directory) throws IOException {
            File[] files = directory.listFiles();
            if (files == null) {
                throw new IOException("not a readable directory: " + directory);
            }
            for (File file : files) {
                if (file.isDirectory()) {
                    deleteContents(file);
                }
                if (!file.delete()) {
                    throw new IOException("failed to delete " + file);
                }
            }
        }
    };

    /**
     * Reads from {@code file}.
     */
    Source source(File file) throws FileNotFoundException;

    /**
     * Writes to {@code file}, discarding any data already present. Creates parent directories if
     * necessary.
     */
    Sink sink(File file) throws FileNotFoundException;

    /**
     * Writes to {@code file}, appending if data is already present. Creates parent directories if
     * necessary.
     */
    Sink appendingSink(File file) throws FileNotFoundException;

    /**
     * Deletes {@code file} if it exists. Throws if the file exists and cannot be deleted.
     */
    void delete(File file) throws IOException;

    /**
     * Returns true if {@code file} exists on the file system.
     */
    boolean exists(File file);

    /**
     * Returns the number of bytes stored in {@code file}, or 0 if it does not exist.
     */
    long size(File file);

    /**
     * Renames {@code from} to {@code to}. Throws if the file cannot be renamed.
     */
    void rename(File from, File to) throws IOException;

    /**
     * Recursively delete the contents of {@code directory}. Throws an IOException if any file could
     * not be deleted, or if {@code dir} is not a readable directory.
     */
    void deleteContents(File directory) throws IOException;
}
